There has been a growing interest in transducer arrangements that provide non-contacting sensing of force or torque transmitted to a transducer element which has a magnetic field associated therewith.
One technology of this general type already established is that dependent on magneto-elasticity. A transducer element subject to torque has a circumferential closed magnetic field stored therein and emanates a torque-dependent external field. Examples of magneto-elastic transducers are disclosed in U.S. Pat. Nos. 5,351,555, 5,465,627 and 5,520,059 and in published PCT application WO99/21150 and WO99/21151. Reference may also be made to published PCT application WO99/56099 which discusses magnetoelastic transducers both for torque and force measurement. Magnetoelasticity is generally understood to be part of a wider phenomenon of magnetization, known as magnetostriction.
It is known that ferromagnetic materials undergo a dimensional change when subject to a magnetizing field. Conversely a magnetized material subject to stress and the resulting strain will be subject to a change in dimension which in turn has an effect on the magnetic field.